Highly Efficient Suzuki-Miyaura Polymerization Enabled by Direct Transmetalation with Boronic Esters

The Suzuki-Miyaura cross-coupling reaction plays a pivotal role in the construction of carbon-carbon bonds, utilizing low-toxicity and readily available organoboron substrates. However, competitive protodeboronation of arylboronic acids has significantly limited its synthetic applications, particularly in the synthesis of optoelectronic polymer materials. Herein, a novel sulfonium salt-mediated Suzuki-Miyaura cross-coupling protocol is developed to synthesize high-quality π-conjugated polymers (CPs). The universality of this method was exemplified by successfully synthesizing twelve CPs with various electrophiles and nucleophiles. Impressively, the synthesized CPs exhibited enhanced optoelectronic properties, e.g., charge carrier mobilities, compared to those synthesized by traditional methods. Experimental and theoretical investigations revealed that direct transmetalation of boronic esters without prior conversion to more reactive intermediates play a critical role in this protocol, thus avoiding the problematic deboronation associated with unstable boronic acids. This method provides an environmentally benign approach to synthesize device-quality CPs.